Fiber bed mist eliminators have found widespread use in applications wherein it is necessary to separate extremely fine aerosols of less than three microns in particle size from a gas or vapor stream. Fiber beds having fibers up to 20 microns in diameter have been found to remove aerosols with a particle size of less than 3 microns with high collection efficiency (e.g., as high as 98-99.9% efficiency).
In fiber bed separator assemblies containing fiber bed mist eliminators, it is desirable to decrease either the number or the circumferential dimension of the mist eliminators, or both, since doing so could decrease the overall size of the separator assembly and, thus, reduce capital costs. However, when attempted in the past, this resulted in more disadvantages than advantages since the pressure drop through the fiber bed walls of the mist eliminator is inversely proportional to the surface area of the fiber beds. In other words, as the surface area of the fiber beds decreases, the pressure drop through these fiber beds increases, and vice versa.
In view of the aforementioned inherent characteristics of fiber bed mist eliminators, if the reduction of the number and/or the circumferential dimension of fiber bed mist eliminators contained in a separator assembly decreases surface area, in order to maintain the output volume of gas the same as that prior to the reduction, it is necessary to increase the input velocity of the gas flowing into the separator assembly. This is undesirable since increasing the input velocity of the gas has a cost associated therewith. Moreover, it is also undesirable to increase the input velocity of the gas entering the separator assembly since doing so will inherently increase the velocity of the gas flowing through the fiber beds of the mist eliminators. This may result in re-entrainment of aerosols captured in these fiber beds.
If, on the other hand, input velocity of gas is maintained at the same level as that prior to the reduction, the output volume of gas from this vessel would decrease. This is also undesirable since it results in production losses which, again, has a cost associated therewith.
Notwithstanding the above, it is also desirable to increase either the number or the circumferential dimension, or both, of the fiber bed mist eliminators in a separator assembly, since doing so would increase the surface area of fiber beds. However, while it is true that increasing the surface area of the fiber beds decreases the pressure drop therethrough, in order to make such an increase, it would be necessary to enlarge the size of the mist eliminators, or the separator assembly, or both. In many instances this is not possible due to space limitations in the plant where the separator assembly is being utilized. However, even if there is adequate space for accommodating a larger separator assembly, it is generally not desirable to construct a larger vessel due to the capital cost associated therewith.
In view of the above, the industry would gratefully accept a fiber bed separator assembly containing mist eliminators which, while maintaining the same circumferential dimension, have a substantially increased fiber bed surface area. Accordingly, one object of the invention is to provide a means for increasing the fiber bed surface area of a mist eliminator without increasing the mist eliminator's circumferential dimension.
Another object of this invention is to reduce the number and/or size of mist eliminators required in a separator assembly without requiring an increase of input energy into the assembly or suffering a reduction of output volume therefrom.
Yet another object of this invention is to increase the output volume of gas without the re-entrainment of the collected liquid phase aerosols back into the output gas stream.
Other objects, aspects and concepts of this invention will become apparent to those skilled in the art upon reading the specification and appended claims which follow.